It has been shown that tumors have developed numerous ways to escape tumor specific immune responses. These mechanisms will ultimately not only enhance tumor growth, but also impair the effect of immune based therapies in cancer. In the past year we were able to complete a study showing how the gut microbiome controls bile acids in the gut, which in turn after absorption into the portal vein control accumulation of NKT cells in the liver. These cells control tumor growth in several animal models.